While it’s rainy, take some time to do maintenance on Watermark sensors

• By Drew Gholson and Dan Roach •

Here it is almost late March and wet again. We noticed some field work and corn planting south of Highway 82 yesterday. I’m sure irrigation is the last thing on most folks’ minds, but here are some watermark things to consider to prepare for irrigation season this summer.

Watermark soil moisture sensors are probably the most widely used sensor here in the Delta. Watermark sensors have a useful life of approximately five years per Irrometer’s web page. Considering the time and effort it takes to replace a bad sensor after installation, dated sensors should be discarded and replaced with new sensors.

The Mississippi State University Irrigation Team routinely inscribes with a permanent marker the date the sensors are put into service. This allows us the opportunity to discard old watermark sensors before they become a problem.

watermark sensors
Watermark sensors

Pre-conditioning of the Watermark sensors is a must!

Watermark sensors must be preconditioned prior to installation. To precondition, slowly wet the sensors by partially submerging them (no more than half way) in water for 30 minutes in the morning, let dry until evening, wet for 30 minutes, let dry overnight, wet again for 30 minutes the next morning and let dry again until evening.

Soak over the next night and install WET. Sensors must be installed wet. Preconditioning the sensors ensures quick response to changing soil moisture conditions. If a sensor is only soaked and then installed, several irrigation cycles must pass before it will respond accurately.

Watermark Sensor Multi-Depth Profile Probe
Watermark Sensor Multi-Depth Profile Probe

Watermark Sensor Multi-Depth Profile Probe.

Multiple Watermark sensors can now be installed on a single piece of PVC pipe using the relatively new 200SS-5-S type sensor. The 200SS-5-S sensor is constructed with the mesh sensor located between two spigot ends for mounting to the PVC pipe.

The MSU Irrigation Team suggests you utse this technique for the 6-inch and 12-inch sensors. We encourage you to try a couple 6-, 12- and 24-inch combinations, but we have had issues installing and retrieving the combination sensor at the 24-inch depth.

More information can be found at the Irrometer web site, https://www.irrometer.com/downloads.html#200ss. Under Support Material, click on the Pipe Install-Single and Multiple Depth Manual.

Dr. Drew Gholson is an irrigation specialist, and Dan Roach is an Extension research associate. Both are based at the Delta Research and Extension Center in Stoneville, Mississippi.

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